This invention is in the field of detectors and controls for the dispensing of fluids, including related methods. The invention has particular application with respect to the dispensing of hazardous fluids, such as automobile gasoline, which are manually dispensed, frequently by untrained members of the public.
Prior methods of controlling the dispensing of gasoline or other fluids have principally included four general types of protective systems. First, there are mechanical switches intended to require physical contact between the pump nozzle and the fill neck of the receiving vessel, such as a fuel tank. An example is the emission-control nozzles required in some states, which require a preset level of contact pressure or physical displacement of an activating mechanism before the pump can be started. Second, there are detectors that check for the presence of a detectable token, such as a magnet, which must be coupled to each receiving vessel. Third, there are interlocking systems designed to permit connection of a specified class of pump nozzles only with members of the matching class of receptacles. A simplistic example of the third type of protective system is the smaller-bore fill necks on the fuel tanks of cars that require unleaded gasoline. Fourth, there are fluid-contact systems, such as those that turn off the pump when the fluid in the receptacle rises to a level so as to contact a tube in the nozzle.
Previously known systems suffer from a variety of problems, however. Protective systems with mechanical or pressure-activated switches can easily be defeated by the user, and such systems cannot tell whether the dispensing nozzle is adjacent to an approved or an unsafe container. Some such switches, particularly pressure activated ones, require cumbersome human effort to initiate and maintain the connection.
Detector-and-token systems and interlock systems, on the other hand, can distinguish between types of containers, but those systems possess the significant disadvantage of requiring modification or replacement of not only the dispensers but also all containers. Thus, they cannot be introduced into an installed base of equipment gradually and yet have any salutary effect. Moreover, such two-part systems tend to have a higher cost and are incapable of verifying the existence of a tight fit between the nozzle and the receptacle.
The above-described fluid-contact systems neither protect against dispensing into the wrong type of container nor ensure a tight fit between the nozzle and the receptacle.